Present direct-view, night-vision, image intensifiers employ photoelectron emission for the primary photodetection process, and thus are limited to visible, near-infrared wavelengths not greater than one micron, e.g., provided by moonlight or starlight, in order to obtain the energy necessary for photoelectron emission. In these devices microchannel plates are typically used to amplify the electrons, which are then directed to a phosphor screen, to provide a visible image.
Imaging systems for middle-infrared radiation (i.e., resulting from heat), which has insufficient energy for photoelectron emission, are indirect, employing arrays of semicondcutor elements connected to display devices by pluralities of wires. These systems are thus complicated, large, heavy, and expensive.